Conventionally, for the purpose of reading and printing image information of documents using an image reading device having a scanner function, some image forming apparatuses such as a copying machine use an image reading device having an ADF (Auto Document Feeder) that sequentially carries documents, while reading the image information, in printing out the image information.
Here, a basic arrangement of a conventional image reading device having the ADF is described below.
For example, as shown in FIG. 9, an image reading device 100 includes a document stacking tray 101, feed rollers 102, a curved transporting path 103, a CCD (Charge Coupled Device) reading unit 104, a CIS (Contact Image Sensor) 105, and an ejection tray 106. The image reading device 100 also includes plural pairs of rollers that carry documents.
The document stacking tray 101 is provided to stack sheets of document (not shown). The feed rollers 102 pick up a document, one at a time, from the stack of documents on the document stacking tray 101, and feed the document to the curved transporting path 103. The curved transporting path 103 is provided so that a transporting path for the documents from the document stacking tray 101 to the ejection tray 106 can be made compact. The curved transporting path 103 has plural pairs of rollers that carry documents.
The CCD reading unit 104 and the CIS 105 read images from the documents.
The CCD reading unit 104 includes an optical unit 107 and a CCD 108. At a reading position C1, the CCD reading unit 104 scales down, using the optical unit 107, an image on the document being transported, and focuses the resultant image on the CCD 108, so as to read the image on one side of the document.
The CIS 105 reads, at a reading position D, an image on the other side of the document being transported, using a linear CCD (not shown) that is substantially equal in width to the transporting path for the documents (slightly wider than a widest possible width of the documents).
The CCD reading unit 104 is also capable of reading, by moving the optical unit 107 to reading positions C1 through C3, an image on a document in a stationary state.
The ejection tray 106 is provided to eject and stack the documents which have been transported and finished with image reading.
With the arrangement above, the image reading device 100 operates as follows.
First, the feed rollers 102 pick up a document from the stack of documents on the document stacking tray 101 one at a time, so as to feed it to the curved transporting path 103. In the curved transporting path 103, the CCD reading unit 104 and/or the CIS 105 read images from the document being transported by the pairs of rollers. It is when double-sided printing is performed that the document is read by the CCD reading unit 104 and the CIS 105. After the images on the document have been read, the document is transported to a document ejecting point 109, and is stacked on the ejecting tray 106.
Referring to publications, the following describes conventional image reading devices that have a basic arrangement similar to that of the image reading device 100 described above.
First, a more specific example of a conventional image reading device is, for example, an auto document feeder for reading documents, disclosed in Japanese Publication for Unexamined Patent Application No. 46472/1997 (Tokukaihei 9-46472; publication date: Feb. 14, 1997).
As shown in FIG. 10, the auto document feeder 200 includes a document stacking tray (stacking tray) 201, a feed roller 202, a curved transporting path (reverse transporting path) 203, a first reading unit 204, a second reading unit 205, a transparent board 206, an ejection tray 207, a transparent document table 208, and a slide bar 209.
In the following, members that have similar functions to those described in the above schematic arrangement are labeled with the same referential numerals, and explanations thereof are omitted here.
The first and second reading units 204 and 205 in the arrangement above are respectively provided to read two sides of each document P being transported. On the transparent board 206, the first reading unit 204 reads the document P being transported.
The transparent document table 208 is not used for reading the document P being transported, but for reading a document, such as an opened book, in a stationary state. The slide bar 209 moves the first reading unit 204 along itself in order to read the stationary document on the transparent document table 208.
In this arrangement, the automatic document transporting device 200 feeds the document P stacked on the document stacking tray 201 to the curved transporting path 203 one at a time, using the feed roller 202. In the curved transporting path 203, the document P so fed is transported along the path. Then, the second reading unit 205 provided on the curved transporting path 203 reads one side of the document P.
Then, on the transparent board 206, the first reading unit 204 reads the other side of the document P that has been fed from the curved transporting path 203. Here, the first reading unit 204 does not move (but is in a stationary state) in reading the document P. Finished with image reading, the document P is ejected to the ejecting tray 207.
With the operations above, plural sheets of document P can be sequentially read while being transported, without being stopped.
In this arrangement, the first reading unit 204 is movable using the slide bar 209. Thus, by moving the first reading unit 204 along the slide bar 209, the document P placed on the transparent document table 208 can be read. As a result, it is possible to manually set and read a page of a book, for example, which cannot be transported.
In this arrangement, the second reading unit 205 is provided midway through the curved transporting path 203, and the first reading unit 204 reads one side of the document not read by the second reading unit. This makes it possible to read both sides of each document by transporting the document only once.
Another specific example of a conventional image reading device is disclosed in Japanese Publication for Unexamined Patent Application No. 32164/1999 (Tokukaihei 11-32164; publication date: Feb. 2, 1999).
As shown in FIG. 11, the image reading device 300 includes a document stacking tray (document tray) 301, a feed roller (pickup roller) 302, a curved transporting path (guide board) 303, first reading means 304, second reading means 305, and an ejection tray (document ejection tray) 306.
In this arrangement, the first reading means 304 and the second reading means 305 are provided for respectively reading two sides of a document being transported.
The first reading means 304, at a reading position E, reads an image of a document being transported, using a CCD 308 through an optical unit 307.
In this arrangement, the image reading device 300, using the feed roller 302, feeds a document P stacked on the document stacking tray 301 to the curved transporting path 303, one at a time. In the curved transporting path 303, the document P is transported along a predetermined path.
Then, the first reading means 304 reads, at a reading position E, one side of the document P that has been fed from the curved transporting path 303 using a transporting roller 309. In so doing, the first reading means 304 reads the document P being transported, without moving the optical unit 307 from the reading position E.
Then, the second reading means 305 reads the other side of the document P being transported, and ejects the document P to the ejection tray 306.
In this manner, plural sheets of document P can be sequentially read while being transported and without being stopped. Moreover, both sides of the document P can be read by the first reading means 304 and the second reading means 305.
In this arrangement, in a case where the document is placed on the glass document table 310, the optical unit 307 is moved with respect to the document (not shown) placed on the glass document table 310, so as to read an image.
Yet another specific example of a conventional image reading device is a document reading device disclosed in Japanese Publication for Unexamined Patent Application No. 27444/1999 (Tokukaihei 11-27444; publication date: Jan. 29, 1999). With reference to FIG. 12, an arrangement of a copying device 400 having the document reading device 410 is described below.
As shown in FIG. 12, the document reading device 410 has a document stacking tray (document stacking table) 401, a separating section 402, a book scanner section 405, a CIS (Contact Image Sensor) 406, and an ejection tray (document ejection tray) 407.
The copying device 400 has a recording section 408 for printing out information read by the document reading device 410.
The separating section 402 includes a separating pad 403 and a separating roller 404. As with the feed roller of the conventional example above, the separating pad 403 and the separating roller 404 are capable of picking up, one sheet at a time, sheets of document P stacked on the document stacking tray 401. In this arrangement, the document P is transported by the separating roller 404, instead of the curved transporting path used in the foregoing conventional example.
The document P that has been transported is read by the book scanner section 405 and the CIS 406. One side of the document P is read at the book scanner section 405, and the other side of the document is read at the CIS 406. Then, the document P that has been read and finished with image reading is ejected to the ejection tray 407.
In this manner, plural sheets of document P can be sequentially read while being transported and without being stopped. Moreover, both sides of each document P can be read by the book scanner section 405 and the CIS 406.
A further specific example of the conventional image reading device is a document transporting device of an image reading device disclosed in Japanese Publication for Unexamined Patent Application No. 34542/1996 (Tokukaihei 8-34542; publication date: Feb. 6, 1996).
As shown in FIG. 13, the document transporting device 500 includes a document stacking tray (document tray) 501, a feed roller (pickup roller) 502, a curved transporting path (document transporting path) 503, a registration roller device 504, a platen roller 505, a platen 506, a scanning device 507, a CCD 508, and an ejection tray 509.
Here, the registration roller device 504 adjusts a position of a front end of the document P being transported, and sends the document P to a reading position at a predetermined timing. The platen roller 505 and the platen 506 transport the document P at the reading position.
In this arrangement, the document transporting device 500, using the feed roller 502, feeds the documents P stacked on the document stacking tray 501 to the curved transporting path 503, one at a time. In the curved transporting path 503, the document P is transported along the path. Then, the front end position of the document P is adjusted by the registration roller device 504, and the document P is sent between the platen roller 505 and the platen 506. In this manner, a reading timing of the document can be adjusted. It is also possible to adjust, for example, an angle of the document P, if the document P is transported on an angle.
Between the platen roller 505 and the platen 506, the document P being transported is read with the CCD 508 via a mirror or the like, which is shown as the scanning device 507. Finished with the image reading, the document P is ejected to the ejection tray 509.
As described above, the document transporting device 500 has such an arrangement in which the front end position of the document P is adjusted by the registration roller device 504, and the document P is transported to the reading position at a predetermined timing. As a result, it is possible to adjust, for example, an angle of the document by adjusting the reading timing, if the document is transported on an angle.
With the foregoing conventional image reading devices and image forming apparatuses, however, there is a problem that a large number of documents cannot be handled, and a thick sheet of document cannot be read appropriately.
Recently, printers and the like having the image reading device have been used in a wider range of applications than before. For example, unlike conventionally, there is a need for handling thick sheets of document. There is also a need for reading larger volume of document in a shorter time, so as to accommodate an increasing amount of information than before.
However, the above arrangements are associated with certain potential problems, as described below.
First, the auto document feeder described in Tokukaihei 9-46472 shown in FIG. 10 is so arranged that the documents P stacked on the document stacking tray 201 are transported by the feed roller 202.
In this arrangement, when a large number of documents P are handled, the height of the stacked documents P on the document stacking tray 201 is gradually lowered as the documents P are sequentially transported. This may cause a problem in picking up the document P with the feed roller 202.
The document stacking tray 201 is provided immediately above the ejection tray 207, covering the ejection tray 207 substantially completely. It is therefore necessary, when handling a large number of documents P, to provide enough space between the document stacking tray 201 and the feed roller 202, and between the ejection tray 207 and the document ejecting point 210, so as to accommodate a large number of documents P or thick sheets of documents P. This increases the height of the auto document feeder 200.
In Tokukaihei 11-32164, shown in FIG. 11, in which the image reading device 300 is described, the publication does not describe any arrangement for ensuring stable supply of documents P in regard to the document stacking tray 301 when handling a large number of documents P or thick sheets of documents P.
In the document reading device 400 described in Tokukaihei 11-27444, shown in FIG. 12, the document stacking tray 401 is provided immediately above the ejection tray 407, covering the ejection tray 407 substantially completely. It is therefore necessary, when handling a large number of documents P, to provide enough space between the document stacking tray 401 and the separating pad 403, and between ejection tray 407 and the document ejecting point 409, so as to accommodate a large number of documents P or thick sheets of documents P. This increases the height of the document reading device 410.
Furthermore, as shown in FIG. 12, the distance between the document stacking tray 401 and the ejection tray 407 depends on a diameter of the separating roller 404. Accordingly, it is necessary to increase the diameter of the separating roller 404 in order to handle a large number of documents P. This might result in great increase in cost of manufacturing, maintaining, and using (in which power is consumed by the rotation) the separating roller 404.
In the document transporting device 500 described in Tokukaihei 8-34542, shown in FIG. 13, the height of documents P stacked on the document stacking tray 501 is gradually lowered as the documents P are sequentially transported. This may cause a problem in picking up a document P by the feed roller 502.
Furthermore, as shown in FIG. 13, the document stacking tray 501 is provided over the ejection tray 509. It is therefore necessary, when handling a large number of documents P, to increase the height of the document transporting device 500, so that the documents P can be stacked thereon.